Huang Xiaowei, Liu Junwei, Ding Junmei, He Qiusheng, Xiong Rui, Zhang Keqin
Yunnan University, Kunming, PR China.
Can J Microbiol. 2009 Aug;55(8):934-42. doi: 10.1139/w09-045.
The Gram-negative bacterium Stenotrophomonas maltophilia G2 was isolated from a soil sample and was found to have high nematotoxic activity against a free-living nematode, Panagrellus redivivus, and a plant-parasitic nematode, Bursaphelenchus xylophilus. The analysis of virulence factors revealed that although the small molecular metabolites participated in nematode killing, the crude extracellular protein extract from the bacterial culture supernatant contributed significantly to its nematocidal activity. An extracellular protease was purified by chromatography, and its effects on degrading purified nematode cuticle and killing living nematodes were confirmed experimentally. Characterization of this purified protease revealed that the application of phenylmethylsulphonyl fluoride, an inhibitor of serine proteases, could completely abolish its proteolytic activity. The results from N-terminal amino acid sequencing showed no similarity with any known serine protease in S. maltophilia, suggesting a novel virulence serine protease was obtained. Our study is the first to show the nematocidal activity of S. maltophilia, and we identified a novel serine protease as an important pathogenicity factor.
嗜麦芽窄食单胞菌G2是一种革兰氏阴性菌，从一份土壤样本中分离得到，被发现对自由生活线虫——秀丽隐杆线虫和植物寄生线虫——松材线虫具有高杀线虫活性。毒力因子分析表明，尽管小分子代谢产物参与了线虫的杀灭，但细菌培养上清液中的粗细胞外蛋白提取物对其杀线虫活性有显著贡献。通过色谱法纯化了一种细胞外蛋白酶，并通过实验证实了其对降解纯化的线虫角质层和杀死活线虫的作用。对这种纯化蛋白酶的表征显示，丝氨酸蛋白酶抑制剂苯甲基磺酰氟的应用可以完全消除其蛋白水解活性。N端氨基酸测序结果显示与嗜麦芽窄食单胞菌中任何已知的丝氨酸蛋白酶均无相似性，表明获得了一种新型毒力丝氨酸蛋白酶。我们的研究首次表明嗜麦芽窄食单胞菌具有杀线虫活性，并且我们鉴定出一种新型丝氨酸蛋白酶是重要的致病因子。
